Geographic Range

Bluntnose darters, Etheostoma chlorosoma, are primarily found in the Mississippi River drainage basin. They may also be found in the Mobile Bay drainage and San Antonio River drainage basin. (Page and Burr, 2005)

Habitat

Bluntnose darters are typically found in sandy, slow running, shallow water. They also can be found occupying areas with scattered debris. Substrates that are somewhat firm also provide a good habitat for bluntnose darters. (Etnier and Starnes, 1993)

Physical Description

Bluntnose darters are pale yellow with a translucent look to them. They have blunt noses and five to six small dorsal saddles. They are also identified by having several small brown “W”’s and “X”’s spread randomly throughout the side of the body. Dorsal and caudal fins are speckled with brown . The suborbital bar is usually present as well as the preorbital bar. The preorbital bar is a distinguishing factor in determining bluntnose darters from Johnny darters, Etheostoma nigrum which are similar in appearance. The preorbital bar connects in the bluntnose darter in contrast to the johnny darter where it does not. The anal fin has one spine and 7-9 soft rays (Etnier and Starnes 1993). The dorsal fin has 8-10 spines and 10-11 soft rays and the caudal fin consists of 13-17 rays. The lateral line is incomplete with a lateral line count of 51-60. The species name E. chlorosoma is broken down chloro = green, soma = body. This name can be misleading because green may only be seen faintly on good specimens. Bluntnose darters can reach a length of 38 to 46 mm during adult stages of life. Males and females appear similar outside of the breeding season, but are sexually dichromatic during the breeding season. ("Wisconsin Department of Natural Resources", 2003; Etnier and Starnes, 1993)

Development

Bluntnose darters start out with an embryonic period, which begins at fertilization. They advance to a larval period when they are able to capture food. Once the organ systems are formed, they enter the juvenile period. They are finally classified as adults when they are able to reproduce (i.e., when gonads become mature). (Moyle and Cech, 2004)

Reproduction

Bluntnose darters are polygynandrous, where females go from one male to the other to maximize their reproductive success. They show dichromatism during the breeding season. Dichromatism is when the species changes color when it is time to attract a mate. During the breeding season males become darker on their belly, dorsal fin, and pelvic fins. They also develop sharp tubercles on the soft rays of their anal and pelvic fins. These breeding tubercles are tiny hard bumps of keratin. While the male courts the female with these rituals, the female usually chooses where to lay the eggs. (Etnier and Starnes, 1993; Moyle and Cech, 2004; Shiels, 2005)

Bluntnose darters are nest spawners. Females select suitable places where the eggs are deposited and fertilized. They use plants or plant debris as suitable places to lay their eggs. They lay their eggs in April or May when the water temperature is suitable for their reproduction success. They usually attach one to three eggs per spawning act. Territoriality is seen in bluntnose darters because they spend time in one specific place guarding the embryo or defending the area. They also show elaborate courtship behaviors. This is shown by the males during breeding season with their elaborate coloration. Females usually produce 230-1000 eggs per reproductive effort. They usually reach maturity at one year of age. (Etnier and Starnes, 1993; Shiels, 2005)

They lay their eggs in April or May when the water temperature is suitable for their reproduction success

Range number of offspring

230 to 1000

Average age at sexual or reproductive maturity (female)

1 years

Average age at sexual or reproductive maturity (male)

1 years

Parental care is provided by the male. This could be due to the greater parental investment the female has in gonadal development when compared to the smaller investment the males make (i.e., sperm vs. ova). Females usually abandon eggs to search for more breeding opportunities. Females have been known to spawn many times during the reproductive season. (Moyle and Cech, 2004; Shiels, 2005)

Behavior

No specific behavioral information was found on bluntnose darters. However Johnny darters, Etheostoma nigrum, have no swimbladder so they are benthic dwelling. They can dart around from rock to rock with quick bursts of speed. (Shiels, 2005)

Predation

Bluntnose darters are small and are likely to be prey for larger species of fish. During the non-breeding season they are light tan with dark brown blotches. This color pattern may provide camouflage from potential predators against the bottom of creeks and streams. (Etnier and Starnes, 1993)

Ecosystem Roles

No specific information was found on bluntnose darters. However darters may have an commensal relationship with freshwater mussels. Commensal relationships occur when one species benefits from the relationship while the other is not affected. They may be integral in the reproductive cycle by having glochidia attach to their gills. (Shiels, 2005)

Economic Importance for Humans: Positive

There is no direct benefit bluntnose darters have toward humans.

Economic Importance for Humans: Negative

Bluntnose darters have no adverse affects on humans.

Conservation Status

Bluntnose darters are threatened in several states along the Mississippi River and adjacent drainages. According to NatureServe Explorer (
http://www.natureserve.org/explorer/), bluntnose darters in Kansas are presumed extirpated, in Wisconsin they are critically imperiled, in Kansas they are imperiled, in Indiana they are vulnerable. Bluntnose darter populations are apparently secure in Kentucky, Illinois, Minnesota, Missouri, Arkansas, Oklahoma, Texas, Tennessee, Alabama, Mississippi, and Louisiana. Their decline could be caused by siltation resulting from agricultural runoff and creeks drying up during periods of drought. ("NatureServe Explorer", 2005; "Wisconsin Department of Natural Resources", 2003)

Contributors

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.